The invention relates to a vehicle structure, in particular for utility vehicles, such as motor vehicles and rail vehicles, in which a covering frame is supported on a loading platform and covers a loading area, it being possible for a roof skin to be attached to moveable bows of the covering frame, and in which at least one flexible reinforcing member is arranged in an upper region of the covering frame in order to stiffen the roof.
In road and rail vehicles and containers known from practice, the load is to be transported as securely as possible. In addition, the loading and unloading is to take place as rapidly as possible in order to be able to return the vehicle etc. as rapidly as possible to its transporting function again. Customary vehicle superstructures enabling the loading platform to be opened up comprise sliding-hoop-type coverings or sliding coverings. A heavy, moveable load may and also has to be anchored in the floor of the loading surface. However, this is not possible with all loaded goods, for example with relatively lightweight piece goods, such as packages, or is at least associated with an increased expenditure of labour, as there is, for example when using nets. Displacing of the load takes place when traveling around tight corners when the unsecured load presses with approximately half of its weight against the side wall of the structure. It has been established that relatively flexible side walls, such as reinforced tarpaulins, may sag laterally by up to 50 cm in such cases.
Roofs with a braided cable in the covering frame are known from practice. Furthermore, reinforced roof tarpaulins are known from practice. However, the latter do not reliably conduct away forces which are being applied, but rather are too elastic, susceptible to wear and expensive.
WO 00 12 337 A1 describes a vehicle structure which is embodied as a sliding-hoop-type covering, in which sliding hoops in the form of an inverted U can be shifted along both longitudinal sides of a loading platform and essentially cover the loading surface. Although a vehicle structure of this type is flexible as regards the loading options, the side walls of the vehicle structure are severely bent outward if the load slips.
WO 00 12 334 A1 describes a sliding covering, in which bows can be shifted via rollers along longitudinal members, which are supported on the loading platform via stakes, to open up a roof opening. Furthermore, side tarpaulins can be displaceably suspended on the longitudinal members. Owing to the extent of the stake, the load in the roof region acts with a large lever on the longitudinal member, in particular in the central region thereof. In the case of longitudinal members which are supported from a plurality of sections of longitudinal-member profiles that are arranged one behind another and are supported in each case on stakes, the supporting on relatively strong transverse members is insufficient to get out the longitudinal members, for which reason the bending outward achieves impermissibly high values.
EP 0 936 093 A1 shows a sliding-hoop-type covering, in which, in the region of the side walls and of the roof, rigid stiffening struts are arranged diagonally between adjacent sliding hoops, it being possible for at least one end of the stiffening elements to be shifted in a guide in such a manner that adjacent sliding hoops can come into contact with one another. A transfer of weight forces which act outward on the side walls is not possible with these stiffening elements.
DE 197 56 865 A1 describes a vehicle structure, in which a covering frame comprising longitudinal members which are supported toward the loading platform by stakes covers a loading area, a roof tarpaulin for covering a roof opening being fastened to bows spanning the two longitudinal members, and it furthermore being possible for side tarpaulins to be fitted in each case into the longitudinal members. To avoid lateral sagging, rigid false floors which stiffen the vehicle structure are fitted into the stakes. Furthermore, the vehicle structure has a complex arrangement of stiffening elements which are designed as a chain or cable and which are fitted, on one side, to a fixed roof part and, on the other side, are fastened to a carriage which can be moved along the longitudinal edge of the roof, as a rule on a somewhat wider end bow which is intended to bring about the parallel guidance of the bows. These stiffening elements are deflected on the bows a number of times from the one side to the other side in each case of the covering frame, diagonally spanning the surface of the loading area, two diagonally extending stiffening elements being deflected in each case at both ends of the same bow, and the stiffening element engaging with both of its ends in the region firstly of the one longitudinal member and secondly of the other of the two longitudinal members. Furthermore, further stiffening elements are stretched parallel to the longitudinal members in ring eyelets in which the diagonally extending stiffening elements are also deflected. Due to the large length of the stiffening elements and because the latter have to be designed to absorb all forces, the stiffening elements have a great thickness, as a result of which the folding of the tarpaulin is impaired. Although, in the known vehicle structure, the stiffening elements bring about a connection between the two longitudinal members, the two longitudinal members buckle in the same direction when subjected to a load, with the result that the vehicle structure buckles in the central region in the manner of a banana—in fact, buckles at two points as the two longitudinal members yield, or even becomes twisted. A further significant disadvantage resides in the fastening of the ends of the stiffening elements to the final bow, since the entire load transferred via the stiffening elements stresses the bearings of the rollers and correspondingly reduces the service life of the rollers. The same applies to the bows on which the eyelets for the deflection of the stiffening elements are provided and the rollers of which have to transfer the entire load acting on the stiffening element to the longitudinal member, which rapidly causes damage to the bearings of the horizontally guided rollers and, accordingly, the stiffening of the roof region is again reduced. Finally, the multiple deflection of the flexible stiffening elements defines a parallelogram of traction that is unable to transfer thrust forces to the opposite longitudinal member to compensate for forces acting on one longitudinal member, and so the stiffening elements expand the one side, as a result of which excessive forces can be introduced into the tarpaulin and the latter can be damaged.